1. Field of the Invention
This present invention generally relates to a pick-up head controller for optical disk drives, and more particularly to a framework, composed of a high-frequency digital controller and a low-frequency digital controller, accomplishing different order types of controllers required by optical head systems, so as to achieve high performance, low cost and easy designing.
2. Description of the Prior Art
Recently, due to the fast development in electro-optic technology, the related techniques of optical disk drives have grown rapidly and compatible with multimedia applications. In particular, CD-ROMs provide a great amount of data storage, and a new disc called DVD-ROM (digital video disk) provides considerably more data storage, reaching data storage capacities of up to 17 GB as compared to 680 MB for a CD-ROM. Such devices have especial usefulness in the storage of archiving data and in the storage of video data, such as full-length movies, and therefore have become the most widely used peripheral components not only in computer-based systems but also in Hi-Fi audio/video systems. At present, in the technical fields according to optical disk drives, most of the Japan-based manufacturers have filed numerous patents related to the controller framework of optical disk drives, so as to avoid violating the rights that have been claimed by the other manufacturers. The key techniques in a control system of an optical disk drive are focus control, tracking control and axis motor control. Generally, the most concerned issues of controller framework design are focused upon easy designing, high performance, and lost cost, and such is hard to achieve.
Nowadays, in order to avoid violating the rights that have been claimed by other manufacturers, most of the Japan-based manufacturers have filed numerous patents related to the controller framework of optical disk drives. Most of the efforts have been made to minimize to number of gates, so as to reduce the cost, but sacrificing the control performance of optical disk drives. Some of the frameworks are structured to be easily designed while not taking the cost into account. Such frameworks are not the best while the performance is to be taken into account. In addition, the optical head controller proposed by Toshiba only provides real roots, in lack of complex roots, of the characteristic equation for control compensation of the controller system, accordingly the compensations in gain and phase can not be improved, resulting in poor frequency response of the controller. In order to overcome the problems mentioned above, the present invention, therefore, provides a controller framework, with cost and performance taken into account.
It is the primary object of the present invention to provide a pick-up head controller for optical disk drives, structured particularly for optimal actuation characteristics of a pick-up head of optical disk drives. Experimental results shows excellent performance in optical systems that high performance, low cost and easy designing can be achieved.
Typically, the key techniques in a control system of an optical disk drive are focus control, tracking control and axis motor control. Therefore, it is another object of the present invention to provide a framework with focus control and tracking control taken into account. The basic principle of the present invention is based upon the sampling rate dependence of response of digital controllers. The controller system according to the present invention can be implemented by using two controllers, i.e., a high-frequency digital controller and a low-frequency digital controller, respectively, so as to achieve compensation in gain and phase at both high frequency and low frequency and, accordingly, a wider band for operation. In addition, the combination of said high-frequency digital controller and said low-frequency digital controller is made by using an averaging unit.